1. Field of the Invention
The present invention relates generally to magnetic recording and/or reproducing apparatus, and more particularly to an apparatus for recording digital data obtained based on an information signal on a magnetic tape by means of a rotary magnetic head device moving to scan the magnetic tape, for reproducing digital data obtained based on an information signal from a magnetic tape, on which the digital data are recorded, by means of a rotary magnetic head device moving to scan the magnetic tape, or for recording digital data obtained based on an information signal on a magnetic tape and reproducing the digital data recorded on the magnetic tape by means of a rotary magnetic head device moving to scan the magnetic tape.
2. Description of the Prior Art
In the field of a video tape recorder (referred to a VTR, hereinafter) used for recording an information signal, such as a color video signal, on a magnetic tape or for reproducing an information signal from a magnetic tape on which the information signal is recorded, there has been proposed to digitalize various signal processing circuits employed in the VTR for the purpose of improving reliability in operation, reducing power consumption, and miniaturizing and lightening the whole body, and a so-called digital VTR, in which an information signal such as a color video signal is converted to digital data to be recorded on a magnetic tape and the digital data obtained base on the information signal are reproduced from the magnetic tape to be converted to a reproduced information signal, has been put to practical use.
In the case of recording and/or reproducing the color video signal by means of the digital VTR, several recording and/or reproducing operation modes are selectively taken as the need arises. For example, when the color video signal subjected to the recording and/or reproduction is a color televising signal according to the NTSC system, PAL system or SECAM system in usual, a LP operation mode in which the color video signal is converted to digital data having the transmission rate of, for example, 15Mb/s to be recorded on the magnetic tape and the digital data having the transmission rate of 15Mb/s obtained based on the color video signal and recorded on the magnetic tape are reproduced from the magnetic tape, and a SP operation mode in which the color video signal is converted to digital data having the transmission rate of, for example, 30Mb/s to be recorded on the magnetic tape and the digital data having the transmission rate of 30Mb/s obtained based on the color video signal and recorded on the magnetic tape are reproduced from the magnetic tape, are selectively taken respectively for achieving a long-playing record on the magnetic tape and for obtaining high quality reproduced pictures based on the reproduced digital data. Further, when a color television signal according to the high definition television system (HDTV system) in which a signal frequency band is extended by a large margin and a horizontal frequency is raised by a large margin in comparison with the color television signal according to the NTSC system is subjected to the recording and/or reproduction, a HD operation mode in which the color video signal is converted to digital data having the transmission rate of, for example, 60Mb/s in view of the extended signal frequency band thereof to be recorded on the magnetic tape and the digital data having the transmission rate of 60Mb/s obtained based on the color video signal and recorded on the magnetic tape are reproduced from the magnetic tape, is taken.
It would be a great convenience to use a VTR in which the LP operation mode, SP operation mode and HD operation mode can be selected appropriately for recording digital date obtained from a color video signal on a magnetic tape and reproducing the digital data from the magnetic tape. However, it seems that such a VTR in which the LP operation mode, SP operation mode and HD operation mode can be selected appropriately has not been proposed previously.
In the case where it is considered to modify a VTR having a pair of rotary magnetic heads disposed at angular intervals of 180 degrees therebetween for scanning alternately a magnetic tape to form oblique record tracks thereon, which has come into wide use at present, so as to be operative to work in each of the LP, SP and HD operation modes selected as occasion demands, the modified VTR is required to be provided with a head driving mechanism for rotating the magnetic rotary heads at each of different three speeds corresponding respectively to the transmission rates of the digital data treated in the LP, SP and HD operation modes, which includes a high speed rotation device for rotating the rotary magnetic heads at an extremely high speed when the HD operation mode is taken, a tape guide mechanism for guiding the magnetic tape along each of different three running paths which are to be made respectively in the LP,SP and HD operation modes, and three digital data processing circuit arrangements for dealing with the digital data in the LP, SP and HD operation modes, respectively. This results in a disadvantage that the modified VTR is very complicated in its construction. Further, in such a modified VTR as mentioned above, it is considerably difficult to keep each of various mechanisms operating with sufficient reliability and the production cost is undesirably increased due to the high speed rotating device.